Membrane vapour concentrator

ABSTRACT

Apparatus for concentrating a vapor including an optional vaporizer, a vapor flow conduit; a counter flow conduit; and an optional humidity controller; wherein at least a portion of the vapor flow conduit and counter-flow conduit define respective opposed sides of a membrane. Also, a method of producing a concentrated active from a solution including an active in a solvent and having a first active-to-solvent ratio, the method comprising the steps of: (1) vaporizing the solution to form a vapor wherein the concentration of active is at about said first ratio, (2) providing a flow of the vapor to a first side of a membrane; and (3) providing an alternate flow of a gas to a second side of the membrane whereby to increase said first active-to-solvent ratio on the first side to a second active-to-solvent ratio greater than the first active-to-solvent ratio.

The present application claims priority to Australian Patent ApplicationNo. 200700504, filed Feb. 2, 2007, and Patent Cooperation TreatyInternational Application No. PCT/AU2008/000108 filed Jan. 31, 2008,which are incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for concentratingvapor, such as may be used for example in disinfecting or sterilizing asurface. The method and apparatus are particularly suited fordisinfecting or sterilizing medical instruments but are not limited tothat use.

BACKGROUND OF THE INVENTION

It is highly desirable to have sterilization processes and apparatusthat avoid the need for temperatures above 60° C. while achieving thehighest possible efficacy in pathogen destruction, especially whentreating occluded, mated and lumen surfaces.

The use of high temperatures leads to complex and costly sterilizationinstruments, and more importantly, can damage many materials. This is aproblem both in terms of patient safety and apparatus cost.

It is desirable that the disinfecting methods use hydrogen peroxide.Hydrogen peroxide at low concentrations is safe to transport, sell, andhandle and is extremely well known, with little or no regulatorybarriers to its use. However, there are problems with those methodsrequiring high concentration hydrogen peroxide as a starting material.For example, commercial vapor and plasma processes use as a startingmaterial corrosive and irritating 60% peroxide solutions requiringspecial packaging and handling precautions.

Any discussion of the prior art throughout the specification should inno way be considered as an admission that such prior art is widely knownor forms part of common general knowledge in the field.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words ‘comprise’, ‘comprising’, and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to”.

BRIEF STATEMENT OF INVENTION

According to a first aspect, the present invention provides apparatusfor concentrating a first vapor in a mixture of a first vapor and atleast a second vapor, the method comprising: a vapor flow conduit; acounter-flow conduit; wherein at least a portion of said vapor flowconduit and said counter-flow conduit define respective opposed sides ofa membrane; and wherein: i) the membrane is selected to favor diffusionof the first vapor over at least the second vapor; and/or ii) theoperating conditions of the apparatus can be selected to favor diffusionof the first vapor over at least the second vapor.

The vapor flow and counter-flow may be in opposite directions, the samedirection, or any other direction, e.g., perpendicular flows.

Preferably, the operating conditions, which can be selected to favordiffusion of one vapor over one or more other vapors in the mixture ofvapors, include temperature or pressure control on either side of themembrane, or humidity or gas flow on an opposite side of the membrane tothe mixture of vapors.

According to a second aspect, the present invention provides apparatusfor concentrating a first vapor in a mixture of a first vapor and atleast a second vapor, the method comprising: a plurality of alternatingvapor flow conduits and corresponding counter-flow conduits; and whereinat least a portion of each vapor flow conduit and an adjacentcounter-flow conduit define respective opposed sides of a membrane; andwherein: i) the membrane is selected to favor diffusion of the firstvapor over at least the second vapor; and/or ii) the operatingconditions of the apparatus can be selected to favor diffusion of thefirst vapor over at least the second vapor.

The alternating vapor flow conduits and counter-flow conduits may be ina layered configuration. Alternatively, they maybe in a concentric,coaxial tubular arrangement.

Each vapor flow conduit comprises an inlet and an outlet. Eachcounter-flow conduit comprises an inlet and an outlet. Preferably, thevapor flow and counter-flow are in opposite directions. However, theymay in the same direction, or any other direction, e.g., perpendicularflow.

Preferably the apparatus further comprises a vaporizer in communicationwith the vapor flow conduit.

Also preferably the apparatus further comprises a humidity control meansfor controlling the humidity of a counter-flow entering the counter-flowconduit.

According to a third aspect, the present invention provides apparatusfor concentrating a first vapor in a mixture of a first vapor and atleast a second vapor, the method comprising: a vapor flow conduit; atleast two counter-flow conduits; and wherein at least a portion of saidvapor flow conduit and said counter-flow conduits define respectiveopposed sides of membranes; and wherein: i) the membranes are selectedto favor diffusion of the first vapor over at least the second vapor;and/or ii) the operating conditions of the apparatus can be selected tofavor diffusion of the first vapor over at least the second vapor.

According to a fourth aspect, the present invention provides apparatusfor concentrating a first vapor in a mixture of a first vapor and atleast a second vapor, the method comprising: at least two vapor flowconduits; a counter-flow conduit; and wherein at least a portion of saidvapor flow conduit and said counter-flow conduits define respectiveopposed sides of membranes; and wherein: i) the membranes are selectedto favor diffusion of the first vapor over at least the second vapor;and/or ii) the operating conditions of the apparatus can be selected tofavor diffusion of the first vapor over at least the second vapor.

In one preferred embodiment, each vapor flow conduit comprises an inletand an outlet, each counter-flow conduit comprises an inlet and anoutlet, and the vapor flow and counter-flow are in the same or oppositedirections.

In another preferred embodiment each vapor flow conduit comprises aninlet and an outlet, and the counter-flow conduit directs a counter flowin a direction at an angle to the vapor flow direction.

According to a fifth aspect, the invention provides a method ofproducing a concentrated active from a solution comprising an active ina solvent and having a first active-to-solvent ratio, said methodcomprising the steps of: (1) vaporizing the solution to form a vaporwherein the concentration of active is at about said first ratio; (2)providing a flow of the vapor to a first side of a membrane; and (3)providing an alternate flow of a gas to a second side of the membranewhereby to increase said first active-to-solvent ratio on the first sideto a second active-to-solvent ratio greater than the firstactive-to-solvent ratio.

According to a sixth aspect, the present invention provides a method forconcentrating a vapor comprising the steps of: (1) providing a flow of avapor of an active in a solvent and having a first active-to-solventratio to a first side of a membrane; and (2) providing an alternate flowof a gas to a second side of the membrane whereby to increase said firstactive-to-solvent ratio on the first side to a second active-to-solventratio greater than the first active-to-solvent ratio.

The concentrated vapor is preferably used to disinfect and/or sterilizean article.

The vapor is preferably a vapor of water and a biocide, i.e., thesolvent is preferably water. Most preferably, the biocide or active is aperoxy compound, most preferably hydrogen peroxide. The presentinvention encompasses any situation where the active-to-solvent ratio isincreased. The active may be present in very small quantities, such as0.1% (or less) of the total active plus solvent and concentrated up tothe point where all or substantially all of the solvent is removed,i.e., 100% active. Hydrogen peroxide is typically sold as a 30 wt % to35 wt % solution in water, so in one embodiment the first active tosolvent ratio is preferably below 35 wt %, and more preferably about 30wt %.

The second active-to-solvent ratio may be any level up to and including100%. In some cases, it is preferably above 60 wt %, and more preferablyabout 70 wt %, and in some preferred embodiments, even above 80 wt % or90 wt %. The counter-flow of gas is preferably provided at a rate andfor a time such that the second ratio is not capable of furtherincrease.

For preference the gas is air, more preferably humidity conditioned air.

The semi-permeable fabric or membrane may be a woven, or non-wovenfabric, or it may be a sheet or film or a combination thereof and may beof a single layer or multilayer construction.

The term “membrane” is used herein where the context permits to includeall such fabrics and membranes having the selected properties. Themembrane may be hydrophobic or hydrophilic in nature.

In this specification where the context permits references to a fabricor membrane include fabrics or membranes suitable for pervaporation aswell those only suitable for simple permeation, and references topermeation include references to pervaporation. Other membranes thanthose described and membranes may be used and may include membranessuitable for pervaporation, or other permeable or semi-permeablemembranes. A highly preferred membrane is Kimguard™ sheet.

In a highly preferred embodiment a peroxide solution having an initialconcentration of at least 3% to 6%, preferably 20% to 35%, and morepreferably 30% to 35%, is vaporized.

Water vapor permeates through the membrane, leaving peroxide vaporbehind. The peroxide in the vapor becomes more concentrated.

The more concentrated peroxide vapor is significantly more effective asa sterilant than prior art hydrogen peroxide vapor possibly because amuch higher concentration of sterilant is obtainable per unit volume.

Air permeating into the vapor flow conduit is sterile because themembrane is not penetrable by micro-organisms.

According to a seventh aspect, the invention provides a processaccording to any one of the preceding aspects wherein the membrane isselected to remove one or more vapors by a process of pervaporation.

Although the invention is herein described with reference to hydrogenperoxide as the biocide, the invention is equally applicable when thebiocide was another peroxide or peroxy compound, or could be used withother known vaporizable biocides or biocides when dissolved in suitablesolvents (which need not be aqueous). Preferably the vapor issubsequently removed by an exterior current of air (or other fluid)adjacent the membrane exterior.

According to an eighth aspect, the invention provides a method fordisinfecting or sterilizing an article comprising the steps of: (1)vaporizing a solution consisting of an active in a solvent and having afirst active-to-solvent ratio: (2) providing a flow of the vapor to afirst side of a membrane; and (3) providing an alternate flow of a gasto a second side of the membrane whereby to increase said firstactive-to-solvent ratio on the first side to a second active-to-solventratio greater than the first active-to-solvent ratio; and (4) contactingthe vapor from step 2 with the article for a time sufficient todisinfect or sterilize it.

In one preferred embodiment the method is conducted at atmosphericpressure or above.

In another preferred embodiment the method is conducted belowatmospheric pressure.

Preferably the counter-flow of gas is provided at a rate and for a timesuch that the second ratio reaches an equilibrium ratio beyond which itwill not increase.

According to a ninth aspect, the invention provides a method fordisinfecting or sterilizing an article comprising the steps of: (1)enclosing the article inside a container having a wall of which at leasta part is a membrane; (2) providing a vapor of an active in a solventand having a first active-to-solvent ratio; (3) providing an alternateflow of a gas to a side of the membrane external to the containerwhereby to increase the first active-to-solvent ratio to a secondactive-to-solvent ratio greater than the first active-to-solvent ratio,and produce a concentrated vapor; and (4) allowing the article to remainin contact with the concentrated vapor for a time sufficient to permitsterilization.

Preferably the membrane is impenetrable by microorganisms and thearticle is sterilized and stored sterile in the container.

In preferred embodiments a hydrogen peroxide solution in water of forexample 35% concentration is firstly vaporized and then the vapor isconcentrated in one chamber by removal of water through a membrane. Theconcentrated vapor is then admitted to another chamber which isdesirably a bag or other container having a membrane as defined as awall or part thereof which is then sealed. This allows the article to besterilized and stored sterile in the second container and permitsremoval of residual hydrogen peroxide and water. Preferably theinvention provides in particular, a vapor having a peroxideconcentration greater than 70 wt % and a water concentration less than30 wt %.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a reproduction of a figure from U.S. Pat. No. 4,797,255 whichshows (curve A) how the boiling point of a water/peroxide mixturechanges with concentration at atmospheric pressure and (curve B) how thegas composition changes.

FIG. 2 is diagram of a first simple embodiment of the present invention.

FIG. 3 is a diagram of a sterilizing apparatus showing thepre-concentrator of the present invention.

FIG. 4 is a more detailed schematic diagram of a sterilizing apparatusshowing the pre-concentrator of the present invention.

FIG. 5 shows a further embodiment of the present invention.

FIG. 6 shows flow patterns of vapor and counter flow in an embodiment ofthe present invention.

FIG. 7 shows the plates that may be used to separate membranes in thoseembodiments of the present invention that use stacked arrays.

FIG. 8 shows results from a membrane concentrator of the presentinvention.

FIG. 9 shows an ultrasonic probe in disinfecting arrangement with anapparatus of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be described in the context of sterilization anddisinfection, but it will be appreciated that the pre-concentrators andpre-concentration methods of the present invention can be used in avariety of fields where concentrated vapors are desired, e.g., drugdelivery, painting/printing, food preparation, materials fabrication,and the like. For example, a number of such processes have beendescribed (U.S. Pat. No. 6,451,254, U.S. Pat. No. 6,673,313 and U.S.Pat. No. 6,655,426) all of which require or involve concentrating ahydrogen peroxide solution by lowering the pressure to preferentiallyevaporate water and removing the water through a vacuum pump prior tovaporizing the solution.

The general pre-concentration process of the present invention takesplace in the context of the following, and can be seen with reference toFIG. 3. An article to be sterilized 1 is placed into a sterilizationchamber 2. The sterilization chamber 2 may be any suitable container,but advantageously is a bag made from a membrane, or a sealed containerhaving a window of a membrane 3.

A pre-concentrator chamber of the present invention 4 is connectedupstream from the sterilization chamber 2. The sterilization chamber 2and pre-concentrator 4 are connected such that flow between thepre-concentrator and sterilizing chamber can be opened or closed by wayof a valve 5.

A vaporizer 6 is connected upstream from the pre-concentrator chamber. Ahydrogen peroxide solution having a starting concentration preferably ofaround 30% to 35% is vaporized.

In the vaporizer, the aqueous hydrogen peroxide is heated, for example,by way of an electrically heated surface, such as a hot plate, and isthen moved away from the vaporization area, for example, by an impeller,blower, or the like. Alternatively, if the aqueous hydrogen peroxide isapplied by a jet directed onto the hot plate, the jet may move thevapor. Alternatively, the vapor may be drawn from the vaporizer by avacuum.

The vaporizer 6 may be fed with sterilant solution on a continuous orintermittent basis from a bulk supply 7, or may be provided with asingle shot dosing system for example a cartridge providing sufficientsolution for one or a plurality of sterilization cycles. Alternatively,a sterilant solution may be provided pre-packed in a capsule which maybe placed in an adapted vaporizer so the capsule is in contact with theheating element of the vaporizer. In this case means are provided forpiercing the capsule so that it is able to release the solution as avapor.

The unconcentrated hydrogen peroxide vapor is then propelled into thepre-concentrator 4 by means of a fan 8 upstream from the vaporizer 6.The vapor formed by the vaporizer 6 is entrained in a gas stream whichin the preferred embodiment is air. It is a significant advantage ofpreferred embodiments of the invention over prior art that they do notrequire a source of filtered sterile air. Instead the invention is ableto draw non-sterile air from the sterilization chamber, and sterilize itwhile recirculating it in use. However, if preferred, aseptic filteredair could be employed. The gas stream is not necessarily air, and couldfor example be an inert gas such as nitrogen, or argon, or could beoxygen or ozone.

In general terms, the pre-concentrator 4 works by exposing the vapor toone face 10 of a membrane 9 while an air current moves across the otherface 11 of this membrane. This leads to preferential evaporation of thewater from the vapor, causing it to become more concentrated withrespect to hydrogen peroxide. As a result of the preferentialevaporation of water, the vapor inside the pre-concentrator 4 becomemore concentrated with respect to hydrogen peroxide with theconcentrations approaching 60% or upwards.

Once formed, the highly concentrated vapor then makes contact with thearticle to be sterilized.

There are two possible preferred modes of operation of thepre-concentrator.

In the first operating mode, which is a batch-wise concentrationprocess, the pathway between the pre-concentrator 4 and sterilizingchamber 2 is shut and a vapor of 35% hydrogen peroxide in water isdriven into the pre-concentrator chamber 4. The pre-concentrator chamberis then isolated (by shutting both valves 5 and 12) and the vapor in thepre-concentrator 4 is then concentrated. Concentration in thepre-concentrator takes place until the maximum concentration of peroxideis achieved. Once this maximum concentration is achieved, the pathwaybetween the pre-concentrator and sterilizing chamber is opened byopening valve 5 and the concentrated vapor is introduced into thesterilization chamber 2.

In the second alternative operating mode, which is a continuousconcentration process, the pathway between the pre-concentrator 4 andthe sterilization chamber 2 is left open. A vapor of a solution of 35%hydrogen peroxide in water enters the pre-concentrator chamber 4 andpasses continuously through the pre-concentrator with fan 8 propulsion.As the vapor passes through the pre-concentrator 4, water ispreferentially removed. Residence time of the vapor in thepre-concentrator is preferably such that the maximum possibleconcentration of peroxide is achieved by the time it exits thepre-concentrator.

The vapor may be introduced into the pre-concentrator 4 continuously orintermittently, for example, 2 seconds on/18 seconds off; or 5 secondson/15 seconds off; over a period of, for example, 2 minutes.

However, regardless of whether batch-wise mode a) or continuous mode b)is employed, or even should some combination of continuous or batch wisemodes be used, the vapor that exits the pre-concentrator 4 and entersthe sterilization chamber 2 is preferably at its maximum achievablehydrogen peroxide concentration.

Once the concentrated vapor is introduced to the sterilization chamber2, it contacts the article to be sterilized 1 and acts upon thepathogens at the surface. The sterilizing chamber 2 may then be sealedfrom the pre-concentrator 4. The concentrated vapor is then allowed tocontact the article to be sterilized. The article to be sterilized canbe stored in the sterilization chamber until needed. This also permitsremoval of residual hydrogen peroxide and water.

To expand on each of the steps, and shown in FIG. 14, the cyclecommences with vaporization of 27% to 35% hydrogen peroxide inside avaporization chamber 6. The vaporizer may function continuously oraccording to an appropriate duty cycle such that vaporization isintermittent. The vapor has the same composition as the bulk solutionfrom which it was derived.

Once produced, the vapor is transported by a blower fan 8 into themembrane concentrator system 4 where it is concentrated by means ofevaporation.

The membrane concentrator 4 is preferably a multi-layered device wherevapor flows over membrane layers which have an alternate airflow on theother side. Selective removal of a portion of the water vapor occurs inthe membrane concentrator due to the differential partial pressures ofwater and hydrogen peroxide. The vapor exits the concentrator either ata predetermined concentration or “terminally” concentrated such that nofurther concentration of hydrogen peroxide will occur.

In one simple embodiment, shown in FIG. 2, the membrane concentrator isa modular, stackable assembly consisting of 4 main components—flowlayer, end plate, tie-rod, and membrane sheet. FIG. 5 shows a preferredstack of concentrator modules.

The flow layers 10 and 11 are defined by thin, square or rectangularplates 12 with a large open area inside and four slots (galleries)running parallel to the outer edges, two of which are connected to theinner space via slots. The orientation of the flow layers (when usingsquare sections), determines the number of layers common to anyparticular gallery. Hence two distinct flow lines may operate a singleassembly through the method of assembly.

The end plates 13 allow connection of external tubing or devices to themembrane assembly and each end plate has two connection points whichcorrespond to two gallery slots. The slots on these end plates form amanifold which directs flow up one particular gallery per connection andthe connections are offset 90 degrees from one another to ensure theyaccess different galleries.

When five flow layers, for example are stacked atop one another withalternate orientations, i.e., 90 degrees to each other, and separated bysheets of membrane material, they form two groups of flow layers, onehaving two flow layers 15 and the other having three separate flowlayers 16 within the block. These flow layers are assigned to eithervapor (15 in the present case) or crossflow/counterflow (16 in thepresent case) connections and through regulation of their flow rates,controlled diffusion is possible.

The tie-rods are used to compress the layers between the end plates andcreate a vapor seal, although any design allowing the blocks to fittogether in suitable sealed arrangement may be used. The membranematerial 9 also acts as a gasket between the layers.

The vapor pressure of hydrogen peroxide at ambient temperatures isnegligible, and water preferentially evaporates in the membraneconcentrator. However, as a precaution against any hydrogen peroxideflow exiting the system, the counter flow is taken directly into thecatalytic destructor module where it is safely treated.

The membrane 9 in the present example is preferably made of Kimguard™sheet, a three layer, non-limiting laminate fabric using polypropyleneand having an inner layer which is hydrophobic and resistant tobacterial penetration. The two outer layers provide abrasion resistanceand strength. As a multi layered fabric it has no actual pore size, butthe fabric is permeable by virtue of microscopic channels which providea tortuous path limiting passage of particles to those of less than 0.2micron, i.e., it is impermeable to micro-organisms below 0.2 microns.This fabric allows hydrogen peroxide vapor or water vapor to permeatethrough the channels of the fabric. The channels do not permit passageof bacteria into the chamber. Kimguard sheet has a hydrostaticrepellency of 3.8 kPa (measure of hydrophobicity) and a crossdimensional tensile load of 70 Newtons and a machine directional tensileload of 130 Newtons.

The membrane 9 may be any other suitable membrane which facilitates theremoval of water while being impermeable by micro-organisms. Otherfabrics and membranes which are permeable by water vapor and hydrogenperoxide vapors and impenetrable by bacteria may be used, for exampleTyvek™ sheet and Spunguard™ sheet (However, Kimguard™ sheet has beenfound to be 2-3 times more permeable to hydrogen peroxide vapor thanTyvek™ under the conditions in which it is used here. As will bediscussed hereinafter other membrane materials such as Nafion™ sheet(which is hydrophilic) and the like may also be employed.

Nafion™ is a copolymer of tetrafluoroethylene and perfluoro 3,6,dioxa-4-methyl-octene-sulphonic acid. Such materials are hydrophilic andhave a very high water of hydration. Nafion™ sheet is able to absorb 22%by weight of water. In this variation the absorption proceeds as a firstorder kinetic reaction. Water molecules pass through the membrane andthen evaporate into the surrounding air until equilibrium with theexternal humidity is reached in a continuous process calledpervaporation. An exterior current flow of air over the external side ofthe membrane provides rapid removal of the moisture from the outsidesurface and speeds the pervaporation process. Unlike simple permeationwherein the molecules merely diffuse through the open pores, inpervaporation the membrane is active in selectively drawing moleculesfrom one side of the membrane to the other, and may do so atdifferential rates for differing types of chemical molecule.

In the embodiments described above the sterilizing agent is a solutionof hydrogen peroxide as a 35 wt % solution in water which acted as thesolvent. Water is the preferred solvent for use with peroxide. Waterboils at 100° C. while hydrogen peroxide boils at above 151° C. atatmospheric pressure. Hydrogen peroxide boils at 151.4° C. at 760 mm.FIG. 1 taken from U.S. Pat. No. 4,797,255 shows (curve A) how theboiling point at atmospheric pressure of a water/peroxide mixturechanges with concentration and (curve B) how the gas compositionchanges. As is shown, pure water boils at 100° C. at atmosphericpressure. It is evident from FIG. 1 that the concentration of hydrogenperoxide in the vapor at below 100° C. is negligible at atmosphericpressure.

Besides water, the solvent could for example be an aqueous ornon-aqueous alcohol chosen in combination with the sterilizing agent tobe used. The addition to water of ethyl alcohol results in an azeotropicmixture which lowers the boiling point of the solvent and this enablesthe water to be “flashed” off at lower temperatures than would otherwisebe possible. The addition of other azeotropic agents would be equallybeneficial. The use of azeotropes to facilitate the removal of a solventsuch as water from the vapor is within the scope of the invention. It isenvisioned that for some biocides non-aqueous solvents or a combinationof suitable solvents could be employed.

In the case of hydrogen peroxide, as the water flashes off, theconcentration of the sterilizing agent increases. If a 35% peroxidesolution is used in the invention as the starting material, theresultant vapor will have a concentration of for example 60% to 80%peroxide. This has the advantage that the starting material can behandled relatively safely, that concentration occurs during the processand that thereafter there is no further need to handle the peroxide.

Solutions of a lower or greater concentration than 35% can be used as astarting material and excellent results have been obtained with hydrogenperoxide solutions of 1% or 3% as well as with solutions of 40%. Whilepreferred embodiments described have employed aqueous solutions ofhydrogen peroxide as the sterilizing agent, solutions of other peroxidesand peroxy compounds can be employed as well as solutions of peroxycomplexes (including non water soluble complexes in organic solvents).Sterilizing agents other than peroxides may also be used in theinvention, including without limitation halo compounds, phenoliccompounds, halogen phenolic compounds and other known biocides, withappropriate choice of solvent.

In an example in which the article to be disinfected is the part of anultrasonic probe 20, for example a probe of a type insertable into abody cavity for diagnostic purposes, the part of the probe 20 to betreated is enclosed in a chamber 2 (as exemplified in FIG. 9). In thiscase the chamber is a specially shaped chamber designed so that thewhole article need not be in the chamber, only that part of the probewhich is to be treated being enclosed. The probe can be suspended insidethe chamber by means of a seal around the gland where the power cordenters the probe.

The vapor is then transported into chamber 2 where it is applied to atarget surface. The ultrasound device may be inserted into the chambervia any of the panels on the device. One possible entrance is from thetop via a screw top lid into which the cord of the device is damped andheld in place on insertion into the chamber. Passage of the vapor fromthe concentrator to the chamber is regulated by a check valve 5. Checkvalves 5 and 12 can control whether the device operates batchwise,continuously or by some combination of both.

If the device operates batchwise, the valve 5 is opened at theappropriate time after the concentration has occurred.

If the device is operated continuously, the valve remains open, with theflow rates and residence times of the vapor calibrated beforehand to beat a maximum when exiting the chamber.

Typically, the chamber 2 is constructed of a heat conductive metal suchas stainless steel or aluminum. Various coating may be applied to theinterior of the chamber such as Teflon to reduce the risk of peroxidebreakdown. The disinfection chamber is electrically heated using heatertrace wire applied to the conductive metal surface. Alternatively, or inaddition, heated air can be blown into chamber. Chamber atmosphere tosupply the blower is made-up from another chamber connection which isplaced on the opposite side of the chamber to the inlet. The chamberitself is isolated from the generation and recirculation circuit bymeans of valves which engage once the vaporization cycle is complete(about 1-1.5 min). This isolation from the adjoining circuit is called“suspended time” or more commonly “hold” time.

The surface of the object 1 to be treated is exposed to the vapor for atime sufficient to sterilize the surface. The resulting concentratedvapor is highly effective at penetrating mated surfaces, and treatingoccluded surfaces which are not directly exposed.

The chamber 2 may be formed fully of a membrane or fabric or may have awall of which at least a part is a membrane or fabric may be of anysuitable shape and design having regard to the requirements of theprocess herein described and can be sealed in any manner impenetrable bymicro organisms. Other membranes or fabrics can be selected based on theteaching herein provided. The container may be permanently connected tothe vaporizer circuit or may be able to be connected and disconnected bya tube and spigot connection, by suitable connectors or other means.

Once the suspended time is complete (approx 1-2 minutes), the systemmoves into catalytic destruction mode or simply “empty”. It is in thiscycle that a suction fan engages which pilots (opens under pressure) acheck valve that connects to the chamber while another valve allowsfresh air to enter the chamber at a controlled rate. This cycle movesthe vapor into the catalytic destructor module where a catalyst is usedto convert the hydrogen peroxide into harmless water vapor and oxygen.The catalytic destructor module is composed of metal oxide baked ceramichoneycomb layers sandwiching similarly treated ceramic beads packaged ina suitable container. The amount of catalyst is proportional to theamount of peroxide extracted from the chamber as well as the flow ratefrom the chamber. Completion of this cycle takes approximately 1 minuteand upon completion, the chamber may be accessed to retrieve thedisinfected target device. It is understood that the time to achievesterilization is more onerous and may take significantly longer.

In some preferred embodiments, the vapor density in the vapor passingfrom the pre-concentrator to the sterilization chamber may be measuredby passing an infra red beam across the connecting conduit to a detectorand measuring the beam attenuation. The infra red is preferably of afrequency which registers peroxide vapor if any. A knowledge vaporcomposition, temperature and residence time allows certification of theresult if desired.

The pre-concentrator can be operated in such a manner that it alwaysoutputs vapor comprising peroxide at a predetermined theoretical maximumconcentration, thereby avoiding the need to determine the concentrationof peroxide at any point of the sterilizing process.

Although the invention has been herein described with reference tohydrogen peroxide as the sterilizing or disinfection agent, theinvention could use other peroxides, peroxy-compounds, or complexes ofeither. Other classes of biocide could be used including withoutlimitation halogenated biocides, phenolic biocides and quaternarycompound biocides and it may be advantageous to use solvents other thanwater. Likewise, although the invention has been herein exemplifiedprimarily with reference to starting solutions having 35% peroxide,other starting concentrations can be employed, although concentrationsbetween about 20% and 35% are preferred.

The principles herein taught could be applied to concentrate theperoxide in such vapor processes by permeation or pervaporation througha membrane, without the need for pressure reduction.

1. Apparatus for concentrating a vapour comprising: a vapour flowconduit; a counter-flow conduit; and wherein at least a portion of saidvapour flow conduit and said counter-flow conduit define respectiveopposed sides of a membrane, wherein said apparatus operates such thatsaid membrane can be selected from a group consisting of selective ornon-selective membranes.
 2. Apparatus according to claim 1 furthercomprising a vaporizer in communication with the vapour flow conduit. 3.Apparatus according to claim 1 or 2 further comprising humidity controlmeans for controlling the humidity of a counter flow entering thecounter-flow conduit.
 4. Apparatus according to any one of claims 1 to 3comprising: a plurality of alternating vapour flow conduits andcorresponding counter-flow conduits; and wherein at least a portion ofsaid each vapour flow conduit and an adjacent counter-flow conduitdefine respective opposed sides of a membrane.
 5. Apparatus according toany one of claims 1 to 4 wherein alternating vapour flow conduits andcounter-flow conduits are in a layered configuration.
 6. Apparatusaccording to any one of claims 1 to 4 wherein alternating vapour flowconduits are in a concentric, coaxial tubular arrangement.
 7. Apparatusaccording any one of claims 1 to 3 for concentrating a vapourcomprising: a vapour flow conduit; at least two counter-flow conduits;and wherein at least a portion of said vapour flow conduit and saidcounter-flow conduits define respective opposed sides of membranes,wherein said apparatus operates such that said membrane can be selectedfrom a group consisting of selective or non-selective membranes. 8.Apparatus according to any one of claims 1-3 for concentrating a vapourcomprising at least two vapour flow conduits; an alternate flow conduit;and wherein at least a portion of said counter-flow conduit and saidvapour flow conduits define respective opposed sides of membranes,wherein said apparatus operates such that said membrane can be selectedfrom a group consisting of selective, or non-selective membranes. 9.Apparatus according to any one of the preceding claims wherein eachvapour flow conduit comprises an inlet and an outlet, each counter-flowconduit comprises an inlet and an outlet, and the vapour flow andcounter-flow are in the same or opposite directions.
 10. Apparatusaccording to any one of claims 1 to 7 wherein each vapour flow conduitcomprises an inlet and an outlet, and the counter-flow conduit directs acounter flow in a direction at an angle to the vapour flow direction.11. A method of producing a concentrated active from a solutioncomprising an active in a solvent and having a first active:solventratio, said method comprising the steps of: (1) vaporizing the solutionto form a vapour wherein the concentration of active is at about saidfirst ratio, (2) providing a flow of the vapour to a first side of amembrane; and (3) providing an alternate flow of a gas to a second sideof the membrane whereby to increase said first active:solvent ratio onthe first side to a second active:solvent ratio greater than the firstactive:solvent ratio, wherein said membrane is selected from a groupconsisting of selective or non-selective membranes.
 12. A method forconcentrating a vapour comprising the steps of (1) providing a flow of avapour consisting of an active in a solvent and having a firstactive:solvent ratio to a first side of a membrane; and (2) providing analternate flow of a gas to a second side of the membrane whereby toincrease said first active:solvent ratio on the first side to a secondactive:solvent ratio greater than the first active:solvent ratio,wherein said membrane is selected from a group consisting of selectiveor non-selective membranes.
 13. A method according to claim 11 or 12wherein the active is a biocide and the concentrated vapour is used todisinfect and/or sterilize an article.
 14. A method according to any oneof claims 11 to 13 wherein the solvent is water.
 15. A method accordingto any one of claims 11 to 14 wherein the active is hydrogen peroxide ora peroxy compound.
 16. A method according to according to any one ofclaims 11 to 15 wherein the first active to solvent ratio is below 35 wt%.
 17. A method according to any one of claims 11 to 16 wherein thesecond active:solvent ratio is above 60 wt %.
 18. A method according toany one of claims 11 to 17 wherein the counter-flow of gas is providedat a rate and for a time such that the second ratio reaches anequilibrium ratio beyond which it will not increase.
 19. A methodaccording to any one of claims 11 to 18 wherein the gas is air orhumidity conditioned air.
 20. A method according to any one of claims 11to 19 wherein the fabric or membrane is a woven, or non-woven fabric, ora sheet or film or a combination thereof and of a single layer ormultilayer construction.
 21. A method according to any one of claims 11to 20 wherein the membrane is hydrophobic.
 22. A method according to anyone of claims 1 to 21 wherein the membrane is Kimguard.
 23. A methodaccording to any one of claims 11 to 22 wherein the membrane is suitablefor pervaporation.
 24. A method according to any one of claims 11 to 23wherein the vapour is an aqueous peroxide vapour having an initialconcentration of from 6%-35 wt % of peroxide.
 25. A method according toaccording to any one of claims 11 to 24 wherein the membrane is selectedto remove one or more vapours by a process of pervaporation.
 26. Amethod for disinfecting or sterilizing an article comprising bringing asuitable biocidal solution concentrated by a method according to any oneof claims 9 to 25 into contact with the article as a vapour.
 27. Amethod for disinfecting or sterilizing an article comprising the steps(1) vaporizing a solution consisting of an active in a solvent andhaving a first active:solvent ratio, (2) providing a flow of the vapourto a first side of a membrane; and (3) providing an alternate flow of agas to a second side of the membrane whereby to increase said firstactive:solvent ratio on the first side to a second active:solvent ratiogreater than the first activer solvent ratio, and (4) contacting thevapour from step 2 with the article for a time sufficient to disinfector sterilize it, wherein said membrane is selected from a groupconsisting of selective or non-selective membranes.
 28. A methodaccording to claim 27 when conducted at atmospheric pressure or above.29. A method according to claim 27 when conducted at below atmosphericpressure.
 30. A method according to according to any one of claims 27 to29 wherein the counter-flow of gas is provided at a rate and for a timesuch that the second ratio reaches an equilibrium ratio beyond which itwill not increase.
 31. A method for disinfecting or sterilizing anarticle comprising the steps of (1) enclosing the article inside acontainer having a wall of which at least a part is a membrane; (2)providing a vapour of an active in a solvent and having a firstactive:solvent ratio, (3) providing, an alternate flow of a gas to aside of the membrane external to the container whereby to increase thefirst active:solvent ratio to a second active:solvent ratio greater thanthe first active:solvent ratio, and produce a concentrated vapour; and(4) allowing the article to remain in contact with the concentratedvapour for a time sufficient to permit sterilization, wherein saidmembrane is selected from a group consisting of selective ornon-selective membranes.
 32. A method according to claim 31 wherein themembrane is impenetrable by microorganisms and the article is sterilizedand stored sterile in the container.